1. Field of the Invention
The present invention relates generally to interlocking fasteners and, more particularly, to automotive fuel tank hanger straps used to secure fuel tanks to automobile underbodies.
2. Description of the Related Art
Automotive fuel tanks are generally supported and attached to the automobile underbody by a pair of hanger straps. These straps extend from underneath the fuel tank to supporting members located on either side of the fuel tank. Often the fuel tank sits in a saddle to protect it from being inadvertently punctured. Channels formed in the bottom of the saddle help locate the straps underneath the saddle and prevent lateral movement of the straps.
Typically, each of the straps have a bolt hole at one end and a somewhat T-shaped fastening head at the other end. This head is connected to the remainder of the strap by a narrower neck portion. The fastening head is designed to be slipped through an opening in the supporting member so that the neck is within the opening. The strap is then shifted slightly to move the neck to a narrower portion of the opening so that shoulders on the head engage the backside surface of the supporting member to prevent removal of the head under tensioning of the strap. The fastening head thereby locks its end of the strap in place. The remaining free end of the strap is then secured to the same or another supporting member via a bolt inserted through the bolt hole. By designing the length of the strap between the fastening head and the bolt hole to be slightly less than the length of the path along which the strap extends, the strap can be tensioned upon tightening of the bolt to prevent the head from moving to the larger portion of the opening and thereafter slipping out of the opening.
The use of a fastening head at one end is preferable to securing that end by a separate bolt and nut because it reduces the number of parts required and simplifies assembly of the automobile. One end of the strap is connected to the automobile underbody simply by slipping the fastening head into the opening, rather than having to align clearance holes in the strap and supporting member through which a bolt must then be inserted and secured by a nut on the backside of the supporting member.
Usually, the fastening head is a unitary portion of the strap and is formed from within the longitudinal margins of the strap to reduce the amount of scrap material produced during manufacturing. The dimensions of the head and neck are selected in accordance with a variety of factors, such as the material used and the expected maximum and cyclic stresses.
One problem which arises with these fastening arrangements is that they do not provide as good protection against inadvertent disconnection of the straps from the supporting members as does a separate bolt and nut assembly. More specifically, if a strap momentarily loses its tension, the fastening head and neck of the strap could slip back to the larger part of the opening in the supporting member through which the head could then slip out. Thus, it would be advantageous to provide a fuel tank hanger strap which includes a fastening arrangement that provides a greater degree of protection against inadvertent disconnection than prior fastening arrangements.
Examples of fasteners designed for other applications are disclosed in U.S. Pat. Nos. 1,405,516, issued Feb. 7, 1922 to C. A. Humphreys, 1,893,537, issued Jan. 10, 1933 to G. R. Cruze, 3,290,743, issued Dec. 13, 1966 to M. P. Hanson, 3,894,707, issued Jul. 15, 1975 to R. A. H. Heard, 4,094,487, issued Jun. 13, 1978 to R. A. H. Heard, and 4,367,572, issued Jan. 11, 1983 to A. L. Zielenski. However, none of these patents provide a fastening arrangement to address the aforementioned problems peculiar to fuel tank hanger straps.